Tractors and other vehicles used in farming operations must be operated precisely to obtain uniform rows during planting and to harvest crops efficiently. Typically tractors used for planting rows of crops are operated manually by an operator who drives the tractor along each row to be planted. The operator must be very careful in order to get uniform rows of planted crops. It is difficult for an operator of a tractor to maintain precise positioning of the tractor relative to rows which have already been planted since the operator has no reference other than the position of the row which was most recently been planted to use as a guide. In addition, it is difficult to maintain the concentration necessary to obtain straight rows, particularly since concentration often decreases with each passing hour and minute of planting.
One prior art method for obtaining uniform rows includes the placement of stakes on each side of a planned row. The operator uses the first stake to precisely align the tractor prior to the planting of the row, the operator then drives the tractor towards the stake at the opposite end of the row, sighting the stake to obtain the desired alignment, this method gives the driver a way to assure that each row is started at the right location and gives the operator a guide for properly aligning the tractor. However, since the tractor is still controlled by an operator who must concentrate in order to obtain good alignment, this process still produces rows of crops that are not precisely aligned.
Another prior art method for obtaining uniform rows includes the use of a sighting bar which extends horizontally from the side of the tractor. This sighting bar is positioned over the previously planted row so as to align the tractor with the previous row. This method gives relatively good results as long as the driver is diligent in maintaining the required alignment. However, when the operator does not precisely align a row, each subsequent row is also misaligned. This results in rows that have dips and turns in each row. Often, due of the difficulty of maintaining precise alignment, where the preceding row deviates, the row being planted deviates even more, causing a variance that increases with each row planted.
In an attempt to make the job of planting easier on the operator, manufacturers of tractors have recently attempted to integrate automated guidance controls for tractors. Guidance controls for tractors typically incorporate a method for position determination such as use of a global positioning system. However, other position determination systems may also be used. These guidance control systems typically include a position determining system for determining position and a vehicle control system for controlling the steering of the vehicle. One method for position determination involves the use of satellites of the US Global Positioning System (GPS) to determine position. The guidance system typically also includes a vehicle control system operable in response to an operator input mechanism. In one such system, the operator positions the tractor at the beginning of a row in response to feedback on a display.
The display may indicate the position of the vehicle or indicate the direction that the operator must move in order to properly determine the appropriate starting point for a row. Once the operator is properly positioned and is ready to start planting a row, he operates the operator input device so as to activate the automatic steering control feature of the guidance control system. The automatic steering control feature of the guidance control system operates the steering of the tractor so as to maintain proper alignment of the vehicle as a row is planted. After traversing the length of the row, the operator disengages the automatic steering control feature of the guidance control system by operation of the operator input device. The operator then turns the tractor around and positions it to start the next row
Though the guidance control system produces precisely aligned rows, problems may result due to the fact that the operator cannot control the tractor. When the guidance control system is in the automatic steering control mode, the user cannot steer the tractor. Typically, only by manually disengaging the automatic steering control feature of the guidance control system may the operator obtain control of the vehicle. In order to disengage the automatic steering control feature of the guidance control system, the operator must look down and operate one or more keys, and/or levers, and/or buttons. Often when collision with an obstacle such as a tree trunk, a rock, or another vehicle is imminent, there is insufficient time to perform the required steps, resulting in the tractor hitting the obstacle.
What is needed is a way to make guidance control systems more safe. In particular, what is needed is a way to allow an operator to disengage the automatic steering control feature of a guidance control system quickly in order to avoid obstacles. The present invention meets the above needs.